Walking along the Northumberland Shore one evening this summer, a phycologist of my acquaintance showed me a little trick of nature that sort of blew my mind.

He called me to the water’s edge and told me to stir the water with my feet. So I did. And the most amazing thing appeared: flecks of light in the water. When I splashed again, the flecks lit up again, wriggling like little sparks of fire through the dark water.

The phycologist – a pedant at heart – explained that this is bio-luminescence. Tiny little marine organisms called dinoflagellates emit light when disturbed. If there are enough of these organisms, the bio-luminescence will light up an entire wave. Satellite photos have captured huge areas of bio-luminescence in the ocean, something sailors used to call the “milky sea.”

You’ve probably seen a fire fly display bioluminescence. But on this night it was in the water. It was like a magic trick only there was no trick. It was real.